CODEWITHSUNDEEP
c++eclipsetemplates
Spring19981
Spring19981

Reputation: 77

overloading error for C++ template function

I am trying to do some practice with function templates as in the following example:

#include <iostream>
using namespace std;

template <class T>
T max(T a, T b)
{
    return a > b ? a : b;
}

int main()
{
    cout << "max(10, 15) = " << max(10, 15) << endl;

    retun 0;

}

But I got the following errors. Could anybody recognize where the problem is? 

..\src\main.cpp:59:40: error: call of overloaded 'max(int, int)' is   
ambiguous
cout << "max(10, 15) = " << max(10, 15) << endl;
                                    ^
..\src\main.cpp:16:3: note: candidate: 'T max(T, T) [with T = int]'
 T max(T a, T b)
^~~
In file included from c:\mingw\include\c++\8.1.0\bits\char_traits.h:39,
             from c:\mingw\include\c++\8.1.0\ios:40,
             from c:\mingw\include\c++\8.1.0\ostream:38,
             from c:\mingw\include\c++\8.1.0\iostream:39,
             from ..\src\main.cpp:9:
c:\mingw\include\c++\8.1.0\bits\stl_algobase.h:219:5: note:         
candidate: 'constexpr const _Tp& std::max(const _Tp&, const _Tp&) 
[with _Tp = int]'
max(const _Tp& __a, const _Tp& __b)

I am sorry I am new to templates. Thanks for your help.

Upvotes: 1

Views: 146

Answers (2)

Quimby
Quimby

Reputation: 19213

Your usage of templates is correct, but the compiler complains that there already is a function called max with same arguments.

It's full name would be std::max, but because you wrote using namespace std its just max and compiler cannot know which function to call.

Solution is not to use using, see Why is "using namespace std" considered bad practice? .

Upvotes: 4

P0W
P0W

Reputation: 47814

using namespace std; is the issue

Please stop using that, see why

The iostream header includes another header file that pulls std::max, giving a compiler error.

Upvotes: 2

Related Questions